An embodiment is a method including forming a raised portion of a substrate, forming fins on the raised portion of the substrate, forming an isolation region surrounding the fins, a first portion of the isolation region being on a top surface of the raised portion of the substrate between adjacent fins, forming a gate structure over the fins, and forming source/drain regions on opposing sides of the gate structure, wherein forming the source/drain regions includes epitaxially growing a first epitaxial layer on the fin adjacent the gate structure, etching back the first epitaxial layer, epitaxially growing a second epitaxial layer on the etched first epitaxial layer, and etching back the second epitaxial layer, the etched second epitaxial layer having a non-faceted top surface, the etched first epitaxial layer and the etched second epitaxial layer forming source/drain regions.
Legal claims defining the scope of protection, as filed with the USPTO.
4. The method of claim 1, wherein after epitaxially growing the first epitaxial layer on the first fin adjacent the gate structure and before etching back the first epitaxial layer, a top surface of the first epitaxial layer has first facets, wherein the etching back the first epitaxial layer removes the first facets, and wherein after etching back the second epitaxial layer, the etched second epitaxial layer has a non-faceted top surface.
5. The method of claim 4, wherein the non-faceted top surface of the source/drain region is level.
7. The method of claim 6, wherein a first vertical thickness of the source/drain regions over the first fin is greater than a second vertical thickness of the source/drain regions between the first fin and the second fin.
8. The method of claim 7, wherein the first vertical thickness is twice the second vertical thickness.
12. The method of claim 11, wherein the first source/drain region forms an air gap between a top surface of the isolation region and the first source/drain region between the first and second recessed fins.
13. The method of claim 11, wherein after epitaxially growing the first epitaxial layer on the recessed first fin and the recessed second fin and before etching the first epitaxial layer, a top surface of the first epitaxial layer has first facets, wherein the etching the first epitaxial layer removes the first facets, and wherein after etching the second epitaxial layer, the etched second epitaxial layer has a non-faceted top surface.
15. The method of claim 11, wherein a first vertical thickness of the source/drain regions over the first fin is greater than a second vertical thickness of the source/drain regions between the first fin and the second fin.
16. The method of claim 11, wherein the first and second etch processes each comprises hydrochloric acid as a precursor.
18. The method of claim 17, wherein the non-faceted top surface of the source/drain regions in an area between adjacent fins is higher than top surfaces of the fins.
19. The method of claim 17, wherein the first and third facets have a 111 orientation, and wherein the second facets have a no orientation.
20. The method of claim 19, wherein the non-faceted top surfaces have a 100 orientation.
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October 21, 2019
March 7, 2023
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